Oxidizing sulfur dyes on cellulose with sodium iodate or potassium iodate

ABSTRACT

Method for oxidizing sulfur dyes on natural or regenerated cellulose textile fibers comprising contacting said fibers having thereon at least one sulfur dye in reduced form with an aqueous, acid, oxidizing solution comprising water, acetic acid and XIO3, wherein X is Na or K.

United States Patent 1191 Weston Nov. 27, 1973 OXIDIZING SULFUR DYES ONCELLULOSE WITH SODIUM IODATE OR POTASSIUM IODATE [75] Inventor: CharlesDouglas Weston, Charlotte,

[73] Assignee: Martin Marietta Corporation, New

York, N.Y.

[22] Filed:' July 6, 1971 21 App]. No.: 160,174

[52] US. Cl. 8/37, 8/21 A, 8/21 B,

8/2] C, 8/82, 8/1 Q [51] Int. Cl.... C09!) 49/00, C09b 49/10, D06p 1/30[58] Field of Search 8/37, 82, 1 Q

{56] References Cited UNITED STATES PATENTS 2,484,300 10/1949 Mayhew..8/37X 4 1933 Dreyfus et al. 8/64 12/1941 Fryer et al. 8/l08 OTHERPUBLICATIONS Knecht et al., Principles & Practice of Textile Printing,1952, pp. 589590 Primary Examiner-George F. Lesmes AssistantExaminer-Patricia C. lves Attorney-John A. Crowley, Jr. et al.

[5 7] ABSTRACT 1 Claim, No Drawings OXIDIZING SULFUR DYES N CELLULOSEWITH SODIUM IODATE 0R POTASSIUM IODATE The present invention relates toa method for oxidizing sulfur dyes on natural or regenerated cellulosetextile fibers.

Generally speaking, the method of the present invention may be describedas in the method for oxidizing sulfur dyes on natural or regeneratedcellulose textile fibers comprising the step of contacting natural orregenerated cellulose textile fibers having thereon at least one sulfurdye in reduced (leuco) form with an aqueous, acid oxidizing solutioncomprising water, acetic acid and an oxidant, whereby the dye isoxidized and fixed on the fibers, the improvement characterized in thatsaid oxidant is sodium iodate or potassium iodate.

By far the most popular prior art method for oxidizing sulfur dyes ontextiles is with the use of aqueous sodium bichromate and acetic acidoxidizing agent, commonly called the chrome and acid method.

However, the chrome and acid method has a number of disadvantages,including the following. With many sulfur dyes on cotton or regeneratedcellulose, chrome and acid produces dyeings having a harsh hand or fee],which causes excessive wearing of needles and fiber fracture duringsewing and necessitates use of lubricants during yarn and raw stockdyeing to soften the harshness. Natural and regenerated cellulosetextile fibers dyed with sulfur dyes, wherein chrome and acid are used,are not easily rewettable, which necessitates use of wetting agents insubsequent wet finishing operations. Residual chrome and acid is noteasily washed away from dyeings, and it is customary to soap the fibersat the boil during such washing. Chrome does not permit the best clarityof shade with many sulfur dyes, probably because of the formation of ametal complex between the chrome and those sulfur dyes. That latterproperty also causes some such dyeings to have less stability to shadechange following washings, as the metal complex is gradually washed awayleaving a clearer dyeing. Finally, and most important, use of chrome andacid causes stream pollution problems, as bichromate is reportedlytoxic, and stream pollution control authorities in some areas are nowbeginning to demand changes from past practices of bichromate disposal.

Aqueous hydrogen peroxide is another commercially used prior art oxidantfor oxidizing sulfur dyes on natural and regenerated cellulose textilefibers.

The major disadvantages associated with peroxide oxidation of sulfurdyes follow. The wash fastness of the resulting dyeings is considerablyless than when chrome and acid is employed. Not all sulfur dyes,particularly those made by sulfurizing 4-hydroxydiphenylamine, can befully oxidized to stable shades with peroxide. Concentration of hydrogenperoxide in the oxidizing bath is both critical to the fastnessproperties of the resulting dyeing and troublesome to control. Hydrogenperoxide does not spontaneously oxidize most sulfur dyes to their fullydeveloped shade, and the time lag between application of the aqueoushydrogen peroxide and oxidation (fixation) of the dye causes loss of dyefrom the fibers, particularly in jig dyeing.

A few textile finishing plants in the United States have recentlyadopted aqueous potassium ferricyanide as the oxidizing agent for sulfurdyes. The primary difficulties with potassium ferricyanide are a slighttime lag between application and dye oxidation, leading to some dye lossfrom the fiber.

The method of the present invention overcomes some of the above priorart disadvantages and provides additional advantages, all of which willbe discussed later herein.

The following is a more detailed description of the method of thepresent invention.

Textile fibers used in the method of the present invention may be in anydesired form, such as knitted or woven fabric, yarn, ball warps,non-woven fabric or raw stock.

According to the method of the present invention, an aqueous, acid,oxidizing solution comprising water, acetic acid, and XIQ, wherein X isNa or K, is contacted with natural or regenerated cellulose textilefibers having thereon at least one sulfur dye in its reduced (leuco)form, and the reduced sulfur dye is oxidized by the iodate ions, whileon the fibers, to the oxidized form of the sulfur dye. Thus, the dye isfixed (insolubilized) upon the fibers, and a dyeing results.

As used herein, the term sulfur dyes is defined as those dyes which maybe applied in a reduced (leuco) state to cotton fibers from solutionscontaining sodium sulfide, or sodium hydrosulfide, or sodiumpolysulfide, and which dyes have affinity for cotton, and which dyes maybe subsequently oxidized on the fibers, and which dyes contain divalentsulfur in the form of thiol or alkali metal thiolate when in theirreduced state.

The present process may be used in dyeing or printing textile fibers.The sulfur dye may be applied to the fibers in any desired manner, suchas by jig, pad, beck, printing roller or yarn package dyeing machine.The sulfur dye may be first applied to the fibers in reduced or oxidizedform, but in the latter case the oxidized dye must be converted to itsreduced form prior to contact with the oxidizing solution.

If desired, the fibers may be optionally batched for a period of time,steamed or dried to facilitate penetration of the dye into the fibers,or to assist in reducing the dye. They also may be rinsed with water toremove excess reducing agent.

The fibers having thereon sulfur dye in reduced form are then contactedwith the oxidizing solution to oxidize and fix the dye on the fibers,such as by immersing the fibers in the oxidizing solution.

The oxidizing reaction is spontaneous, and almost no time elapsesbetween contact of the fibers having reduced sulfur dye thereon with theoxidizing solution and development of the full shade of the dyeing(oxidation).

The aqueous, acid, oxidizing solution comprises water, acetic acid, andX10 wherein X is Na or K. If desired, the oxidizing solution may alsocontain a fiber wetting agent, e. g. a non-ionic or anionic surfaceactive agent.

The quantity of X10 wherein X is as above defined, which will be used inthe aqueous, acid, oxidizing solution depends primarily upon the amountof dye used. Enough of the XIO will be used to oxidize the quantity ofleuco form dye on the fibers. For most purposes, an aqueous, acidoxidizing solution comprising 0.75-7.5 gms. XIO /liter of water, whereinX is Na or K, will be suitable for use in the present method. It issuggested that the oxidizing solution be adjusted to about pH 34.5 withacetic acid.

The oxidizing solution may be at about -l80F., and preferably aboutl40F., when it contacts the fibers having reduced dye thereon.

Following oxidation of the sulfur dye, the fibers may be washed anddried in conventional manner.

In some instances, polyacrylic and polyamide textile fibers may be dyedby the above method, depending upon the particular sulfur dye selected.Blends of natural or regenerated cellulose textile fibers withpolyacrylic, polyamide or synthetic linear polyester textile fibers maybe used in the present method, in which case the natural and regeneratedcellulose will be dyed, the polyacrylic and polyamide dyed by somesulfur dyes and not by others, and the polyester substantiallyunaffected by the process.

The method of the present invention has a number of advantages, some ofwhich follow.

The waste aqueous sodium, potassium and iodate ions, and iodinemolecules, resulting from the present system are non-toxic in thequantities involved, and a substantial improvement over theobjectionable bichromate resulting from the chrome and acid method.Hence, stream pollution problems will be improved.

Dyeings without a harsh hand and which are easily rewettable without theaid of a rewetting agent, result from the method of the presentinvention, which are improvements over the chrome and acid method.

Residual iodate ions, iodine molecules, and acid are washed off fibersmore easily than the chrome and acid residue.

Many dyeings which have been prepared by the present method have betterclarity of shade than those in which chrome and acid is employed,particularly sulfur blue dyeings.

The degree of wash fastness of natural and regenerated cellulose dyeingsmade from sulfur dyes depends upon the particular sulfur dye and theoxidizing agent employed. The wash fastness of dyeings prepared by thepresent process varies from acceptable to very good. Generally speaking,the wash fastness (staining and color loss) of dyeings made by theprocess of the present invention is superior to those resulting fromhydrogen peroxide oxidation, and in some instances equal to and in otherinstances slightly inferior to dyeings made by the chrome and acidmethod. However, dyeings prepared by the present method are more stableagainst shade change on washing than dyeings made with peroxide orchrome and acid.

Light fastness of dyeings prepared by the present process appears equalto light fastness of dyeings made by the chrome and acid method.

All sulfur dyes can be oxidized to stable shades by the present process,including those sulfur dyes made by sulfurizing 4-hydroxydiphenylamine,in contrast to the hydrogen peroxide oxidation method.

I have titrated aqueous N/2O Na S reducing agent against aqueous N/2Ochrome and acid and against aqueous N/20 NaIO and acid, and measured theoxidation potentials at various levels during the titration. Theoxidation potential of the chrome and acid gradually diminishes in asubstantially straight line relationship as Na s is added to the chromeand acid. Surprisingly, the oxidation potential of the aqueous NalOincreases slightly as the first Na S is added, then is maintained at afairly constant and high level while most of the Na S is added, andfinally diminishes greatly and rapidly, but only after consumingsubstantially more Na s than did the chrome and acid. The practicaleffects of this surprising phenomenon are that during continuousprocessing the use of iodate insures a high oxidation potential and auniform developed shade throughout the continuous process, withoutprecise control of iodate concentration, whereas the maintenance of auniform oxidation potential and shade with chrome and acid is difficult.

The following are illustrative examples of the present invention inwhich all parts are by weight unless otherwise specified. References inthe examples to C. 1. names and numbers for sulfur dyes are to COLOURINDEX, Second Edition, Supplement 1963, published by The Society ofDyers and Colourists, Yorkshire, England.

Example 1 A dye solution consisting of 4 02. C. I. Leuco Sulphur Black1, C. I. No. 53185, per gallon of water is padded at 150F. onto wovencotton shirting weighing 4 oz./sq. yd. The fabric is squeezed to permitpercent wetpick-up based on fabric weight; steamed at 230F. for 1minute; passed through four wash boxes containing water at ambienttemperature and equipped with exit nip rolls; immersed in an oxidizingsolution at F. consisting of 2.0 gms. NalO and 2.5 ml. glacial aceticacid/liter of water for 30 seconds; rinsed well with water and dried.

An excellent black dyeing results.

Example 2 A Gaston County yarn dyeing machine is loaded with cottonyarn. The yarn is boiled ofi in conventional manner with 1 percentacetic acid and 2 percent sulfonate wetting agent by running 30 minutesat 200F.; the bath is dumped and the machine is recharged with 1 percentsodium sulfide; the machine is run 10 minutes at 120F., whereafter thereis added to the machine and to the above solution 15 percent of a 200gm./liter aqueous solution of pre-reduced C. I. Leuco Sulphur Yellow 4,C. I. No. 53160, in 4 parts over 20 minutes at 120F. The temperature isthen raised to F. at which time 40 percent sodium chloride is added in 4parts over 20 minutes. The machine is run an additional 30 minutes at160F. Without dropping the bath, overflow washes using water at 90F. aregiven with circulation through the yarn package in the outside-indirection until the overflow is clear. The pump direction is thenreversed and washing continued with an inside-out direction until theoverflow is clear. The drain is then closed and a circulating wash at120F. is given for 10 minutes. The bath is dropped, the machine refilledwith water at 120F. to which is added 0.75 gms./liter K10 and 1.0gm./liter glacial acetic acid which is run for 10 minutes at 120F. Thisbath is then dumped, the yarn washed with water and the water dumped,and the machine refilled with water at 180F. to which is added a 0.5percent tetrasodium pyrophosphate and 1 percent synthetic detergentwhich is run for 10 minutes at 180F. The bath is dropped and the yarn isgiven a running water rinse until clear.

All the percentages given above in this example are based on the weightof the cotton fiber being dyed. The ratio of solution to fiber is 10:1by weight. All of the chemicals given above are added to water to formaqueous solutions prior to adding to the machine.

An excellent yellow dyeing results on the yarn.

Example 3 This example is the same as Example 1 above, except Example 4This example is the same as Example 1 above, except that the dyesolution consists of 2.4 oz. C. l. Leuco Sulphur Blue 13, C. I. No.53450, per gallon of water; except that the amount of NaIO is reduced to0.75 gmsJliter; and except that the oxidation bath is at 50F.

An excellent blue dyeing results.

Example This example is the same as Example 1 above, except that wovenregenerated cellulose fabric weighing 3 oz./sq. yd. is substituted forthe cotton fabric of Example 1; and except that the dye solutionconsists of 4.8

oz. C. I. Leuco Sulphur Green 3, C. l. 535 70, per gallon of water.

An excellent green dyeing results.

Example 6 This example is the same as Example 1 above, except that thedye solution consists of 0.8 02. C. l. Leuco Sulphur Blue 7, C. I. No.53440, per gallon of water.

An excellent blue dyeing results.

What is claimed is:

1. In the method for oxidizing sulfur dyes on natural or regeneratedcellulose textile fibers comprising the step of contacting natural orregenerated cellulose textile fibers having thereon at least one sulfurdye in reduced form with an aqueous, acid oxidizing solution comprisingwater, acetic acid and an oxidant, the improvement wherein said oxidantis sodium iodate or potassium iodate.

